Spelling suggestions: "subject:"reaction intermediate""
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MASS SPECTROMETRY FOR REACTION MONITORING AND REACTION ACCELERATIONXingshuo Chen (11790056) 19 December 2021 (has links)
<p>Mass spectrometry-based
techniques have been widely used in reaction monitoring due to their high
sensitivity and ability to offer structure information by tandem mass
spectrometry. We applied nanoelectrospray mass spectrometry (nanoESI-MS) to
simultaneously monitor pre-catalysts, catalytic intermediates, reagents, and
products of palladium catalyzed Suzuki-Miyaura cross-coupling reactions. A set
of Pd cluster ions related to the monoligated Pd (0) active catalyst is
detected, and its deconvoluted isotopic distribution reveals contributions from
two neutral molecules. One is assigned to the generally accepted Pd (0) active
catalyst, seen in MS as the protonated molecule, while the other is suggested
to correspond to a deactivated form of Pd catalyst. Oxidative stress testing of
the synthetic model catalyst XPhos Pd cyclo-octadiene, performed using oxygen
and Fe(III), supported this assignment. Thus, the make-up of the monoligated
set of Pd (0) ions appears to indicate the oxidation state of the system. The formation
and removal of the oxidative addition intermediate during the catalytic cycle
was monitored to provide information on the progress of the transmetalation
step. </p>
<p> </p>
<p><a>Recently,
microdroplets created by ambient ionization source have been used as reaction
vessels to accelerate organic reactions. Field desorption mass spectrometry
under ambient conditions is applied to study solution-phase organic reactions
in micro-volumes. Compared to nanoelectrospray, it is noteworthy that radical
cations and formation of radical cation products are observed. Three reactions,
the hydrazone formation by phenyl hydrazine and indoline-2,3-dione, the
Katritzky reaction between a pyrylium salt and anisidine, and the Hantzsch
synthesis of 1,4-dihydropyridine, were investigated by this system and reaction
acceleration was observed to different extents. The increase in rate relative
to that for the corresponding bulk reactions is attributed to solvent
evaporation which increases concentration, and to the increase of
surface-to-volume ratio with enhanced interfacial reaction rate constants. Later work in this thesis describes explicit
solvent calculations to study the energies and structures of the hydrazone
formation reaction from phenylhydrazine and indoline-2,3-dione in acidic
methanol with density functional tight binding (DFTB) methods. Additionally,
the thesis covers MS based methods for determination of isoaspartate and
aspartate in peptide by gas-phase chemistry and detection of
S-nitrosoglutathione in exhaled breath condensate sample.</a></p>
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Mechanistic Studies on the Reactions of Vitamin B12 Complexes with the Nitroxyl (HNO) Donors Angeli's Salt and Piloty's AcidSubedi, Harishchandra 29 July 2014 (has links)
No description available.
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Analysis of Protein Three-Dimensional Structures and Capture of Organic Reaction Intermediates by Mass SpectrometryZheng, Qiuling 04 August 2016 (has links)
No description available.
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Synthesis and photophysics of porphryins linked to metal carbonyl unitsAspley, Catherine J. January 2000 (has links)
No description available.
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Approaches to cyclobutane containing cage compoundsRogers, Bruce January 1999 (has links)
No description available.
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Reakční intermediáty v homogenní zlatné katalýze / Reaction intermediates in homogeneous gold catalysisShcherbachenko, Elena January 2016 (has links)
The presented master thesis is devoted to the investigation of reaction intermediates in homogeneous gold catalysis. Electrospray ionization mass spectrometry (ESI-MS) was used as the primary research technique in this study. Delayed reactant labeling was used as the main method. I have focused mainly on the hydration of 1-phenyl-1-propyne catalyzed by the gold complex [Au(IPr)(MeCN)]BF4 (IPr = 1,3-bis(2,6-di-iso-propylphenyl)imidazol-2- ylidene). I have detected two main intermediates containing one or two gold atoms, respectively (monoaurated and diaurated intermediate). I have obtained rate constants for the degradation of the reaction intermediates and their half-lives. I have derived kinetic isotope effects for the formation and the decomposition of the detected intermediates. I have shown that the kinetics of the degradation of both intermediates is identical, therefore I conclude that hydration of alkynes catalyzed by gold complex [Au(IPr)(MeCN)]BF4 proceeds most probably via neutral monoaurated intermediates. These neutral intermediates are detected by ESI-MS as protonated (monoaurated intermediate) or tagged by a second gold cation (diaurated intermediate). Key words: gold catalysis, reaction intermediates, electrospray ionization, mass spectrometry.
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The use of scanning electrochemical microscopy for the detection and quantification of adsorbed intermediates at electrodesRodriguez Lopez, Joaquin, 1983- 07 December 2010 (has links)
Scanning electrochemical microscopy (SECM) was used for the study and characterization of catalytic and electrocatalytic processes occurring at electrodes. The Surface Interrogation mode (SI-SECM) was introduced for the detection and quantification of adsorbed intermediates and products of catalyzed chemical and electrochemical reactions at noble metals (Pt, Au). In SI-SECM two micro electrodes (i.e. an SECM tip and a substrate of the desired material) are aligned concentrically at a micrometric distance where SECM feedback effects operate. A contrast mechanism based on feedback effects allows for the detection of reactive adsorbed intermediates at the substrate: the SECM tip generates a reactive homogeneous species that “micro-titrates” the substrate adsorbates to yield an electrochemical signal that contains information about the amount of intermediate and about its kinetics of reaction with the redox mediator. The technique was used for the study of the reactivity of three model small adsorbates: 1) the reactivity of adsorbed oxygen on Au and Pt with a reducing mediator was explored and suggested the detection of “incipient oxides” at these surfaces; kinetic parameters of the reactivity of Pt oxides with mediators were obtained, fit to theory and used to explain observations about the electrocatalytic behavior of Pt under anodizing conditions; 2) the reactivity of oxidizing mediators with adsorbed hydrogen on Pt was studied and showed the cation of N,N,N,N-tetramethyl-p-phenylenediamine (TMPD) to be a successful interrogation agent, the detection of hydrogen generated by the decomposition of formic acid on Pt at open circuit was investigated; 3) electrogenerated bromine was used to catalytically interrogate carbon monoxide at Pt, this reaction was previously unreported. The mentioned applications of SECM were validated through the use of digital simulations of diffusion in the complex SECM geometry through flexible commercial finite element method software. / text
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A Novel Mass Spectrometry Method to Study Reaction Intermediates and Development of AuTeCDs for Scavenging ROS in Live CellsXu, Chang January 2020 (has links)
No description available.
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Matrix Isolation Studies of Photochemical and Thermal Reactions of Cyclic Organic Substrates with Chromyl Chloride and Ozone/O AtomsHoops, Michael Dean 25 August 2008 (has links)
No description available.
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Mechanistic studies on the degradation of cyanobacterial toxins and other nitrogen containing compounds with hydroxyl and sulfate radical based Advanced Oxidation TechnologiesAntoniou, Maria G. 08 April 2010 (has links)
No description available.
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